PROJECT 3 ? SUMMARY/ASTRACT HCC incidence and mortality rates are rapidly increasing in the United States, in part due to the epidemics of obesity and diabetes. The greatest increase has been seen in Hispanics in South Texas. Our studies in the Cameron County Hispanic Cohort (CCHC) established from a community with high rates of obesity (52%) and diabetes (28%), showed that chronic liver disease is also common (42%). Non-alcoholic fatty liver disease (NAFLD), the most common liver manifestation of obesity and diabetes, ranges from simple steatosis to non- alcoholic steatohepatitis (NASH). Advanced fibrosis is the main risk factor for HCC in NAFLD patients. We first reported a 3.5% prevalence of advanced fibrosis in CCHC, with a remarkable population attributable fraction of 65% for central obesity. We then implemented liver fibrosis screening in CCHC, using vibration-controlled transient elastography (VCTE), and reported a 14% prevalence of clinically significant fibrosis (stage ?F2). The prevalence of significant liver fibrosis reached 28% in obese and diabetic subjects. Strong associations between gut microbiota changes and progression of NAFLD to NASH and HCC, have been reported and bile acids are important mediators in this gut-liver cross-talk. Furthermore, we identified fatty acids as non-invasive markers of NAFLD activitiy and liver fibrosis in patients with NAFLD. Our long-term translational goal is to determine the contributing factors and molecular drivers of liver fibrosis in obese and diabetic Hispanics in South Texas, the community in the United States with the highest rate of HCC, and identify those at risk of progression to advanced fibrosis and therefore HCC, so preventive interventions can be implemented. We hypothesize that demographic, clinical, and molecular (microbiome features, bile acids, fatty acids) parameters are associated with liver fibrosis stages in obese Hispanics with diabetes. We hypothesize further that a model based on these parameters will predict fast fibrosis progression and thus increased risk for HCC development in these subjects. We will enroll 900 obese and diabetic CCHC subjects and 500 obese and diabetic Hispanic patients scheduled for liver biopsy at participating liver clinics. All study participants will be screened for liver fibrosis with VCTE and plasma bile acids, plasma fatty acids and gut microbiome features will be measured. Study participants identified with fibrosis ?F2 will be followed prospectively and liver fibrosis will be again assessed by VCTE and/or liver biopsy at 36 months. In Aim 1, we will determine the performance of VCTE against liver fibrosis for fibrosis staging in the study population. We will also determine the prevalence and risk factors associated with liver fibrosis in obese and diabetic Hispanics in South Texas. In Aim 2, we will identify the molecular markers among those measured that are associated with liver fibrosis stages. In Aim 3, we will identify a model incorporating selected parameters from Aim 1 and molecular markers from Aim 2 in predicting fast liver fibrosis progression in obese Hispanics with diabetes. The impact of this project would be reduction of HCC mortality rates through early intervention and prevention.